Image courtesy of http://www.solar-green-wind.com/archives/tag/solar-power-2009
Image courtesy of http://www.027ws.com/what-is-a-solar-panel.html
Every day the Sun has the potential to rid the world’s need of fossil fuels and power the globe solely on its power. Energy is the capacity of an object to do work. Every amount of work that is done and every movement resulting from that work requires energy. The Sun produces a gigantic amount of energy; a vast amount of it radiates onto planet Earth. The Sun bombards the Earth with 1,000 watts of energy per every square meter of the Earth’s surface per day. Photovoltaics is the process of turning the Sun’s electromagnetic radiation into usable and consumable energy. In summary, this process is accomplished by using solar cells to create an electrical current and electrical field to produce electricity. Solar cells are created when a layer of silicon that has been n-doped, or has had electrons added to it, is placed over a different layer of silicon that has been p-doped, or has had electrons taken away. When electromagnetic radiation from the sun comes into contact with the n-doped layer of silicon, it causes the n-doped silicon to release its excess electrons that then flow towards the p-doped layer of silicon. When the electrons reach a point of equilibrium between the two layers, it creates an electrical field. This energy is harvested by placing flow points, or points where electricity enters and exits a system, at the top and bottom of the solar cell. The continued assault of electromagnetic radiation from the Sun continuously disrupts the equilibrium, creating a constant current. The electric field acts as a diode drawing the energy to the flow points. This flow of energy is harvested as usable DC (direct current) energy. DC energy can be stored or changed into AC (alternating current) energy by use of an AC adapter, which is normally present in most solar energy systems. AC energy is the type that all household appliances require to run and function through an average wall outlet.
Efficiency:
Image courtesy of http://cleantechnica.com/2008/05/10/solar-power-goes-to-extremes-for-5
The efficiency of these solar cells is affected by a large number of variables, some of which include: material, surface area, band-gap energy, and reflectiveness. Silicon is most commonly used as the necessary semiconductor due to its pure crystalline structure. However, pure silicon has to be doped with other minerals to regulate electronic flow. Silicon is highly resistant to the flow of electricity much like rubber; so to gain efficiency, channels for the electricity to flow are added to direct current. This decreases the amount of surface area available for energy conversion and lowers efficiency, but allows solar panels to work the way they do. This is a necessary process since more energy is lost due to resistance than lack of surface area. Also, every material used in solar cells has only a certain diversity of wave lengths of light that it is able to convert into usable energy. Different materials have different light absorption properties. This variable range of wavelengths is called band gap energy. High band gap energy means that there are only a few wavelengths of light that match the properties of the material and release electrons that create an electrical current. A high band gap produces high voltage energy with a low current; a low band gap energy produces low voltage energy with a high current. Reflective properties of the doped compound also change the efficiency of solar panels. Silicon is a reflective material, which means much of the light that reaches it bounces off in the other direction. To counter the defectiveness of light rays that escape the system, an antireflective coating is applied over the top of the panel. The thicker the coating is, the more light will be blocked from the Sun; however, less light that reaches the solar panel will be able to escape after reflecting off of the layers of silicon. The most efficient solar panels find a healthy balance between both reflective coatings and band gap energies.
Other forms of solar energy harvesting:
Image courtesy of http://www.sciencebuddies.org/science-fair-projects/project_ideas/CompSci_p010.shtml
Image courtesy of http://www.cleardomesolar.com/parabolic.html
Solar panels are the common face of solar energy production; although, not all forms of harvesting the sun’s energy are silicon laden and glass-protected. Solar thermal-electric power uses not silicon, but parabolic mirrors to concentrate the sun’s energy to a central point called a receiver. This heats up the receiver to 1000 degrees Fahrenheit on an average sunny day. The receivers are connected to a tank filled with water where the heat and water produce steam that rises and turns a generator, producing electricity. The same effect can be seen when holding a magnifying glass still for long enough in one spot. The solar energy covering the area of the warped glass is being concentrated into one spot that will receive all of the sun’s heat energy for the given area. Magnifying glasses can even heat up one spot enough to catch material on fire! The setback of using mirrors to harvest solar energy is that they must be adjusted every few minutes to receive direct sunlight that will heat up the receivers. While not ideal for homes, solar thermal-electric power plants constantly monitor the less expensive parabolic mirrors and can create energy at the price of twelve cents per kilowatt-hour, (a unit for power usage). Advances in solar thermal-electric power are constantly lowering the price of harvesting energy produced by the sun, and ultimately, making the globe a little greener.
Comparisons against other renewable energy sources:
Image courtesy of http://www.lenntech.com/greenhouse-effect/kyoto-policy-measures.htm
Image courtesy of http://www.tutorvista.com/content/science/science-ii/sources-energy/wind-energy.php
“The surface of the Earth receives an amount of solar energy equivalent to roughly 10,000 times the world energy demand.” (Lysen, 2003) The amount of power the sun gives off is substantial compared to wattage produced by any other form on Earth. Having no harmful by-products or tune-up costs, free energy is irresistible when it comes to the pros and cons of solar energy versus any other form of natural renewable energy sources. First, geothermal energy, or heat energy extracted from under the Earth’s surface, can only produce vast amounts of energy when the geothermal plant is located near the edge of a tectonic plate, where the largest amount of heat is nearest to the Earth’s surface. Comparing the cost of the plant to the amount of energy produced, the value of the energy produced hardly measures up to the initial development. Some geothermal plants even produce greenhouse gases in the conversion of heat to energy, but they do not nearly create the amount of pollution as fossil fuels do. Although it still is not a truly clean form of energy, geothermal energy ranks high as a part of the global search for dependable, renewable energy sources. Next, wind and wave energy both use forces of nature to spin turbines that produce electric power. Both forms, however, are highly dependent on the weather, and therefore are very unreliable because the weather changes constantly. Wind energy has become very efficient and is used in many places around the world in areas that are known to fall victim to high wind speeds due to the weather. Wave energy is still on the brink of research, but is already being used along coastlines to generate electricity and desalinize water for drinking. Something the planet will always have is human garbage. Burning landfill gases and waste creates energy in the form of biomass energy. This method releases harmful carbon dioxide into the air just like fossil fuels do when burned. However, it seems a more viable solution to ridding the land of garbage instead of waiting for the glass, plastics, and rubber found in everyday trash to decompose. While not green to the air, biomass energy is helping to clear land space for better environmental uses. Most of the other forms of renewable energy still have flaws in efficiency, or environmental friendliness. Recognizing that solar energy is truly the best choice for a renewable source is taking us one step further to becoming green.
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Lab Notebook:
Solar Cells Cody Blades Tony Quintana March 23, 2011
Objective:
To determine the best lighting scenario needed for a photovoltaic photocell to produce the most energy (measured in volts).
Safety:
Do not touch heat lamp bulb when hot Do not operate electrical lamp or plug with wet hands
Materials:
solar cell
multimeter
sunlamp
sunlamp stand
protractor
single-ply tissue paper
double-ply tissue paper
Planned Procedure:
Find a room in which no light enters - determined by the output reading of the solar cell to be 0.000V when the lights are off
Place lamp on self-created lamp stand at maximum distance away from the solar cell and plug in the lamp
Connect the multimeter to the output leads of the solar cell and set the multimeter to read voltage
Place the solar panel flat on the bottom of the stand
Place the protractor on the stand so that the center aligns with the middle of the hinge
Turn on the sunlamp and turn off the room light respectively
Measure the voltage output of the solar cell at the angles of: 90, 60, 45, 30, and 0 degrees to the horizontal
Repeat the above process with single and double-ply tissue paper placed halfway between the sunlamp and solar cell
Graph the voltage outputs of the three scenarios on a graph with the y-axis labeled voltage, and x-axis labeled angle
Hypothesis:
If there is no tissue paper between the sunlamp and solar cell and the lamp is perpendicular to the cell (90 degrees), then the voltage output will be the highest.
Actual Procedure:
We found a room in which no light enters so that the output of the solar cell when the lights were off was 0.000V
We attached the sunlamp to the self-made stand at the maximum distance of 3ft. and plugged in the lamp
We connected the output leads of the solar cell to the multimeter and set the multimeter to read voltage
We placed the solar cell flat on the lamp stand
We set the protractor onto the stand so that the center was aligned with where the hinge/angle adjuster rotates
We turned on the sunlamp and turned off the room lights respectively
We wrote down the voltage output of the solar cell with the lamp at: 90, 60, 45, 30, 15, and 0 degrees from the horizontal
We repeated the process with the sunlamp placed at 2ft. and 1ft. away from the solar cell
Around the middle of the experiment readings for 1ft., we noticed a significant drop in the voltage reading after I had moved further away from the stand. We had concluded this was due to the reflectiveness of the bright orange shirt I was wearing during the experiment. Wanting more accurate readings, I changed into a black shirt so that my relevant position had less of an effect the output of the solar cell due to my shirt’s reflectiveness.
The entire experiment was repeated from the 3ft. position, and the new values were recorded in the form of the table below
Solar cell efficiency is based on the percentage of the sun’s power a cell can capture. Since the sun produces 1000 watts of energy per square meter and the average photovoltaic cell is 15% efficient, the maximum voltage our solar cell can output is 0.45v (as stated on the back of the cell). Comparing the voltage readings to the maximum voltage will tell us the percent of the 15% that is being produced.
Table of Contents
Solar Panels and Solar Energy Efficiency
Energy and Solar Cells:
Efficiency:
Image courtesy of http://cleantechnica.com/2008/05/10/solar-power-goes-to-extremes-for-5
The efficiency of these solar cells is affected by a large number of variables, some of which include: material, surface area, band-gap energy, and reflectiveness. Silicon is most commonly used as the necessary semiconductor due to its pure crystalline structure. However, pure silicon has to be doped with other minerals to regulate electronic flow. Silicon is highly resistant to the flow of electricity much like rubber; so to gain efficiency, channels for the electricity to flow are added to direct current. This decreases the amount of surface area available for energy conversion and lowers efficiency, but allows solar panels to work the way they do. This is a necessary process since more energy is lost due to resistance than lack of surface area. Also, every material used in solar cells has only a certain diversity of wave lengths of light that it is able to convert into usable energy. Different materials have different light absorption properties. This variable range of wavelengths is called band gap energy. High band gap energy means that there are only a few wavelengths of light that match the properties of the material and release electrons that create an electrical current. A high band gap produces high voltage energy with a low current; a low band gap energy produces low voltage energy with a high current. Reflective properties of the doped compound also change the efficiency of solar panels. Silicon is a reflective material, which means much of the light that reaches it bounces off in the other direction. To counter the defectiveness of light rays that escape the system, an antireflective coating is applied over the top of the panel. The thicker the coating is, the more light will be blocked from the Sun; however, less light that reaches the solar panel will be able to escape after reflecting off of the layers of silicon. The most efficient solar panels find a healthy balance between both reflective coatings and band gap energies.
Other forms of solar energy harvesting:
Image courtesy of http://www.sciencebuddies.org/science-fair-projects/project_ideas/CompSci_p010.shtml
Comparisons against other renewable energy sources:
Image courtesy of http://www.lenntech.com/greenhouse-effect/kyoto-policy-measures.htm
Image courtesy of http://www.tutorvista.com/content/science/science-ii/sources-energy/wind-energy.php
“The surface of the Earth receives an amount of solar energy equivalent to roughly 10,000 times the world energy demand.” (Lysen, 2003) The amount of power the sun gives off is substantial compared to wattage produced by any other form on Earth. Having no harmful by-products or tune-up costs, free energy is irresistible when it comes to the pros and cons of solar energy versus any other form of natural renewable energy sources. First, geothermal energy, or heat energy extracted from under the Earth’s surface, can only produce vast amounts of energy when the geothermal plant is located near the edge of a tectonic plate, where the largest amount of heat is nearest to the Earth’s surface. Comparing the cost of the plant to the amount of energy produced, the value of the energy produced hardly measures up to the initial development. Some geothermal plants even produce greenhouse gases in the conversion of heat to energy, but they do not nearly create the amount of pollution as fossil fuels do. Although it still is not a truly clean form of energy, geothermal energy ranks high as a part of the global search for dependable, renewable energy sources. Next, wind and wave energy both use forces of nature to spin turbines that produce electric power. Both forms, however, are highly dependent on the weather, and therefore are very unreliable because the weather changes constantly. Wind energy has become very efficient and is used in many places around the world in areas that are known to fall victim to high wind speeds due to the weather. Wave energy is still on the brink of research, but is already being used along coastlines to generate electricity and desalinize water for drinking. Something the planet will always have is human garbage. Burning landfill gases and waste creates energy in the form of biomass energy. This method releases harmful carbon dioxide into the air just like fossil fuels do when burned. However, it seems a more viable solution to ridding the land of garbage instead of waiting for the glass, plastics, and rubber found in everyday trash to decompose. While not green to the air, biomass energy is helping to clear land space for better environmental uses. Most of the other forms of renewable energy still have flaws in efficiency, or environmental friendliness. Recognizing that solar energy is truly the best choice for a renewable source is taking us one step further to becoming green.
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Lab Notebook:
Solar Cells
Cody Blades
Tony Quintana
March 23, 2011
Objective:
To determine the best lighting scenario needed for a photovoltaic photocell to produce the most energy (measured in volts).Safety:
Do not touch heat lamp bulb when hotDo not operate electrical lamp or plug with wet hands
Materials:
Planned Procedure:
Hypothesis:
If there is no tissue paper between the sunlamp and solar cell and the lamp is perpendicular to the cell (90 degrees), then the voltage output will be the highest.Actual Procedure:
Solar cell efficiency is based on the percentage of the sun’s power a cell can capture. Since the sun produces 1000 watts of energy per square meter and the average photovoltaic cell is 15% efficient, the maximum voltage our solar cell can output is 0.45v (as stated on the back of the cell). Comparing the voltage readings to the maximum voltage will tell us the percent of the 15% that is being produced.
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Prezi:
Solar energy on Prezi
Citations: